Base station, terminal apparatus, communication control method and radio communication system

ABSTRACT

To adaptively interleave in accordance with communication channel conditions. Provided is a base station performing radio communication with a terminal apparatus on a communication channel formed by integrating a plurality of component carriers, including a quality acquisition unit that acquires channel quality of the communication channel for each of the component carriers and an interleaver that interleaves data signals transmitted on the communication channel in accordance with at least one of the channel quality acquired by the quality acquisition unit and available situations of communication resources for each of the component carriers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/246,002, filed Aug. 24, 2016, which is a continuation of U.S.application Ser. No. 14/518,338, filed Oct. 20, 2014, which is adivisional of U.S. application Ser. No. 13/517,255, filed Jun. 20, 2012(U.S. Pat. No. 8,885,629, issued Nov. 11, 2014), which is a nationalstage application of International Application No. PCT/JP2011/050014,filed Jan. 4, 2011, which claims priority to Japanese Patent ApplicationNo. 2010-004564, filed Jan. 13, 2010, the contents of each of which arehereby incorporated by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a base station, a terminal apparatus, acommunication control method, and a radio communication system.

BACKGROUND ART

In Long Term Evolution-Advanced (LTE-A), which is the next-generationcellular communication standard that is discussed in Third GenerationPartnership Project (3GPP), introduction of technology called carrieraggregation (CA) has been studied. The carrier aggregation is technologythat forms a communication channel between a user equipment (UE) and abase station (BS, or evolved Node B (eNB)) by aggregating a plurality offrequency bands that are supported in LTE, for example, and therebyimproves communication throughput. Each frequency band included in onecommunication channel that is formed by the carrier aggregation iscalled a component carrier (CC). The bandwidths of frequency bands thatare available in LTE are 1.4 MHz, 3.0 MHz, 5.0 MHz, 10 MHz, 15 MHz, and20 MHz. Accordingly, if five bands of 20 MHz are aggregated as componentcarriers, a communication channel of 100 MHz in total can be formed.

Component carriers that are included in one communication channel in thecarrier aggregation are not necessarily contiguous to one another in thefrequency direction. The mode in which component carriers are arrangedcontiguous to one another in the frequency direction is called acontiguous mode. On the other hand, the mode in which component carriersare arranged not contiguous to one another is called a non-contiguousmode.

Further, in the carrier aggregation, the number of component carriers inan uplink and the number of component carriers in a downlink are notnecessarily equal. The mode in which the number of component carriers inan uplink and the number of component carriers in a downlink are equalis called a symmetric mode. On the other hand, the mode in which thenumber of component carriers in an uplink and the number of componentcarriers in a downlink are not equal is called an asymmetric mode. Forexample, in the case of using two component carriers in an uplink andthree component carriers in a downlink, it can be called asymmetriccarrier aggregation.

Further, in LTE, any one of frequency division duplex (FDD) and timedivision duplex (TDD) can be used as duplex operation. Because thedirection of a link (uplink or downlink) of each component carrier doesnot change in time in FDD, FDD is better suited to the carrieraggregation compared to TDD.

The carrier aggregation technology is described in, for example,Non-Patent Literature 1.

CITATION LIST Non-Patent Literature

Non-Patent Literature 1: “LTE-Advanced and the Evolution to 4G CellularSystems” [online], [searched on Jan. 5, 2010], Internet<URL:http://www.ece.gatech.edu/research/labs/bwn/ltea/projectdescription.html>.

SUMMARY OF INVENTION Technical Problem

If the carrier aggregation technology is used, as described above, radiocommunication can be performed in higher throughput compared to thepast. However, under current circumstances in which many users use radiocommunication services such as packet-based voice calls and real-timevideo delivery, further contrivances to improve communicationcharacteristics are needed to maintain a high service quality level. Inthe framework of IEEE802.11n, for example, improving data communicationcharacteristics by interleaving a series of data signals between twochannels having the bandwidth of 20 MHz is proposed. However, theinterleave between channels in IEEE802.11n is a static interleavefollowing an operation preset for an RF circuit. According to thetechnique of such an interleave, if quality of a portion of channelsdeteriorates or a channel with less available resources is present,expected characteristics may not be obtained. If a technology thatadaptively interleaves in accordance with communication channelconditions, by contrast, communication characteristics can be improvedmore reliably in radio communication accompanied by carrier aggregation.

Thus, the present invention provides a novel and improved base stationcapable of interleaving adaptively in accordance with communicationchannel conditions in radio communication accompanied by carrieraggregation, a terminal apparatus, a communication control method, and aradio communication system.

Solution to Problem

According to an embodiment of the present invention, there is provided abase station performing radio communication with a terminal apparatus ona communication channel formed by integrating a plurality of componentcarriers, the base station including: a quality acquisition unit thatacquires channel quality of the communication channel for each of thecomponent carriers; and an interleaver that interleaves data signalstransmitted on the communication channel in accordance with at least oneof the channel quality acquired by the quality acquisition unit andavailable situations of communication resources for each of thecomponent carriers.

When each of the data signals transmitted on the communication channelis classified into one of two or more classes in accordance with servicequality requirements, the interleaver may mix, into one componentcarrier, a plurality of the data signals each of which is classifiedinto the two or more classes.

When each of the data signals transmitted on the communication channelis classified into one of two or more classes in accordance with servicequality requirements, the interleaver may frequency-interleave the datasignal classified into one class between the plurality of componentcarriers in accordance with at least one of the channel quality acquiredby the quality acquisition unit and the available situations ofcommunication resources.

The interleaver may not distribute bits of the data signals classifiedinto the class in which the relatively high service quality is requiredto the component carrier that does not maintain a predetermined qualitylevel.

The interleaver may distribute bits of each of the data signals to oneor more component carriers having available resources exceeding acertain ratio present therein and maintaining a predetermined qualitylevel.

When bits of the data signal classified into one class are distributedto two or more component carriers, a percentage of distribution of bitsmay be decided in accordance with at least one of the channel qualityfor each of the component carriers and the available situations ofcommunication resources.

When each of the data signals transmitted on the communication channelis classified into one of two or more classes in accordance with servicequality requirements, the interleaver may mix, into one resource block,a plurality of the data signals each of which is classified into the twoor more classes.

The interleaver may further time-interleave each of the data signals.

The interleaver may further space-interleave each of the data signals byusing a plurality of antennas.

According to another embodiment of the present invention, there isprovided a terminal apparatus performing radio communication with a basestation on a communication channel formed by integrating a plurality ofcomponent carriers, the terminal apparatus including: a radiocommunication unit that transmits/receives data signals interleaved inaccordance with at least one of channel quality of the communicationchannel for each of the component carriers and available situations ofcommunication resources for each of the component carriers to/from thebase station.

According to another embodiment of the present invention, there isprovided a communication control method to control radio communicationwith a terminal apparatus on a communication channel formed byintegrating a plurality of component carriers from a base station, themethod including the steps of: acquiring channel quality of thecommunication channel for each component carrier, judging, for eachcomponent carrier, available situations of communication resourcesallocated to the radio communication; and interleaving data signalstransmitted on the communication channel in accordance with at least oneof the channel quality and the available situations of communicationresources.

According to another embodiment of the present invention, there isprovided a radio communication system containing a base station and aterminal apparatus that perform radio communication with each other on acommunication channel formed by integrating a plurality of componentcarriers, wherein the base station includes: a quality acquisition unitthat acquires channel quality of the communication channel for each ofthe component carriers; and an interleaver that interleaves data signalstransmitted on the communication channel in accordance with at least oneof the channel quality acquired by the quality acquisition unit andavailable situations of communication resources for each of thecomponent carriers, and the terminal apparatus includes a radiocommunication unit that receives the data signals interleaved by theinterleaver of the base station from the base station.

Advantageous Effects of Invention

As described above, a base station, a terminal apparatus, acommunication control method, and a radio communication system accordingto the present invention can adaptively interleave in accordance withcommunication channel conditions.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram showing an overview of a radiocommunication system according to an embodiment.

FIG. 2 is an explanatory view exemplifying the configuration ofcommunication resources.

FIG. 3 is an explanatory view illustrating configuration examples ofdata packets.

FIG. 4 is a block diagram exemplifying the configuration of a terminalapparatus according to an embodiment.

FIG. 5 is a block diagram exemplifying the configuration of a basestation according to an embodiment.

FIG. 6 is a block diagram exemplifying a detailed configuration of aradio communication unit according to an embodiment.

FIG. 7A is an explanatory view illustrating a first example ofinterleave processing according to an embodiment.

FIG. 7B is an explanatory view illustrating a second example of theinterleave processing according to the embodiment.

FIG. 7C is an explanatory view illustrating a third example of theinterleave processing according to the embodiment.

FIG. 8 is an explanatory view illustrating a first pattern of mappingbetween component carriers and QoS classes.

FIG. 9 is an explanatory view illustrating a second pattern of themapping between component carriers and QoS classes.

FIG. 10A is an explanatory view illustrating a first example of a thirdpattern of the mapping between component carriers and QoS classes.

FIG. 10B is an explanatory view illustrating a second example of thethird pattern of the mapping between component carriers and QoS classes.

FIG. 10C is an explanatory view illustrating a third example of thethird pattern of the mapping between component carriers and QoS classes.

FIG. 10D is an explanatory view illustrating a fourth example of thethird pattern of the mapping between component carriers and QoS classes.

DESCRIPTION OF EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the appended drawings. Note that,in this specification and the drawings, elements that have substantiallythe same function and structure are denoted with the same referencesigns, and repeated explanation is omitted.

“Description of Embodiments” will be described in the following order:

1. Overview of Radio Communication System

1-1. Overall Image of System

1-2. Configuration of Communication Resources

1-3. Classification of Service Quality Requirements

2. Configuration Example of Apparatus According to An Embodiment

2-1. Configuration Example of Terminal Apparatus

2-2. Configuration Example of Base Station

2-3. Configuration Example of Interleave Processing

2-4. Mapping Between Component Carriers and Classes

3. Conclusion

1. Overview of Radio Communication System

[1-1. Overall Image of System]

FIG. 1 is a schematic diagram showing an overview of a radiocommunication system 1 according to an embodiment of the presentinvention. Reference to FIG. 1 shows that the radio communication system1 includes one or more terminal apparatuses 100 and a base station 200.

The terminal apparatus 100 is positioned inside a cell 202 in whichradio communication services are provided by the base station 200. Theterminal apparatus 100 performs data communication with another terminalapparatus inside or outside the cell 202 via the base station 200 on acommunication channel formed by combining a plurality of componentcarriers (that is, by carrier aggregation). The base station 200provides communication services to the terminal apparatuses 100positioned inside the cell 202 on a communication channel formed bycombining a plurality of component carriers. The base station 200 canalso communicate with other base stations via a backbone link (forexample, the X2 interface). Further, the base station 200 can alsocommunicate with an upper node such as Serving-Gateway (S-GW) and MMEvia, for example, the S1 interface.

[1-2. Configuration of Communication Resources]

FIG. 2 shows the configuration of communication resources in LTE as anexample of the configuration of communication resources to which thepresent invention can be applied. Reference to FIG. 2 shows thatcommunication resources in LTE are divided into individual radio frameshaving the length of 10 msec in a time direction. Further, one radioframe contains 10 subframes and one subframe is formed of two slots of0.5 ms. In LTE, the subframe is the unit in which communicationresources are allocated to each terminal apparatus in the timedirection. The unit is called a Resource Block. One Resource Blockcontains 12 sub-carriers in a frequency direction. That is, one ResourceBlock contains a size of 1 msec×12 subcarriers in a time-frequencyregion. If the bandwidth and the time length are the same, throughput ofdata communication grows with an increasing number of Resource Blocksallocated for data communication. In the radio communication system 1shown in FIG. 1, the base station 200 decides allocation ofcommunication resources to each of the terminal apparatuses 100. Forexample, the base station 200 delivers scheduling information to theterminal apparatus 100 on a broadcast channel of a downlink.

[1-3. Classification of Service Quality Requirements]

In the radio communication system 1, each data signal transmitted on theabove communication channel classified into one of two or more classesin accordance with service quality requirements (hereinafter, referredto as QoS (Quality of Service) requirements) of traffic. Two or moreclasses in accordance with QoS requirements may be, for example, fourclasses (hereinafter, referred to as QoS classes) shown in Table 1. InTable 1, the class name, attribute examples concerning QoS requirementsof the class, and examples of corresponding services are shown for eachof the four QoS classes.

TABLE 1 Example of classification Attribute examples concerning QoSClass name requirements Service examples Conversational Error rate VoIPTransfer delay Video conference Guaranteed bit rate Streaming Error rateReal-time video delivery Transfer delay Guaranteed bit rate InteractiveError rate Web access Database search Background Error rate E-mail SMS

First, the first QoS class is the “Conversational” class. For traffic ofthe “Conversational” class, as an example, three attributes of the errorrate, transfer delay, and guaranteed bit rate are defined as QoSrequirements to be met.

The error rate can be expressed as, for example, an SDU (Service DataUnit) error ratio or a residual bit error ratio. The SDU error ratiorepresents the ratio of SDUs in which an error is detected totransmitted SDUs. The residual bit error ratio is the ratio of bits thatare not detected on the receiving side to transmitted data bits. Thetransfer delay is a delay amount permitted during transmission. Theguaranteed bit rate refers to the bit rate guaranteed to terminalapparatuses by the radio communication system 1. Instead of theguaranteed bit rate (or in addition to the guaranteed bit rate), themaximum bit rate may be used.

As is understood from Table 1, the radio communication system 1schedules communication resources for traffic belonging to the“Conversational” class so that the error rate, transfer delay, andguaranteed bit rate do not fall below predetermined reference values.Examples of services corresponding to the “Conversational” class includethe VoIP (Voice over IP) and video conference.

The second QoS class is the “Streaming” class. Also for traffic of the“Streaming” class, three attributes of the error rate, transfer delay,and guaranteed bit rate are defined as QoS requirements to be met.However, reference values of QoS requirements concerning theseattributes may be different from reference values in the“Conversational” class. Examples of services corresponding to the“Streaming” class include real-time video delivery.

The third QoS class is the “Interactive” class. For traffic of the“Interactive” class, for example, only the error rate is defined as QoSrequirements to be met. Examples of services corresponding to the“Interactive” class include Web access and database search.

The fourth QoS class is the “Background” class. Also for traffic of the“Background” class, for example, only the error rate is defined as QoSrequirements to be met. However, the reference value of the error ratemay be different from the reference value in the “Interactive” class.Examples of services corresponding to the “Background” class include theE-mail and SMS (Short Messaging Service).

Classification of QoS classes shown in Table 1 is only an example. Forexample, independent QoS classes for control signaling such as IMS(Information Management Signaling) may be defined. Stringent (orhigh-priority) QoS requirements can be imposed on QoS classes forcontrol signaling than on the above QoS classes for data signals. Intowhich of these QoS classes to classify each data signal is decided by,for example, individual service applications and is indicated in, forexample, the header of a data packet.

FIG. 3 is an explanatory view illustrating configuration examples ofdata packets that can be transmitted by the radio communication system1. Reference of FIG. 3 shows four data packets 4 a, 4 b, 4 c, and 4 d.

The data packet 4 a is constituted of a header section and a datasection. The data section of the data packet 4 a contains data bits ofthe class Ci. For example, the class Ci may be one ofC1=“Conversational”, C2=“Streaming”, and C3=“Interactive”, andC4=“Background”. That is, in this case, the data packet 4 a is a packethaving only a data signal of a single class.

The data section of the data packet 4 b contains data bits of the classCi and the class Cj. For example, the class Cj may also be one (but isdifferent from the class Ci) of C1=“Conversational”, C2=“Streaming”, andC3=“Interactive”, and C4=“Background”. Thus, data bits of different QoSclasses may be contained in one data packet mixedly.

The data packet 4 c is a data packet distributed over a plurality ofMIMO (Multiple Input Multiple Output) streams. The data section of thefirst MIMO stream among these streams contains data bits of the classCi. The data section of the second MIMO stream contains data bits of theclass Cj. Thus, data bits of different QoS classes may be contained ineach of the data packets distributed over the plurality of MIMO streams.Further, like the data packet 4 d, data bits of two or more differentQoS classes may be contained in each of data packets distributed over aplurality of MIMO streams.

In the present embodiment, the radio communication system 1 performsradio communication accompanied by carrier aggregation in an environmentin which data signals of the plurality of QoS classes can be mixed. Datasignals transmitted between the terminal apparatus 100 and the basestation 200 are adaptively interleaved depending on communicationchannel conditions, as will be described in detail in the nextparagraph.

2. Configuration Example of Apparatus According to An Embodiment

[2-1. Configuration Example of Terminal Apparatus]

FIG. 4 is a block diagram exemplifying the configuration of the terminalapparatus 100 according to the present embodiment. Reference to FIG. 4shows that the terminal apparatus 100 includes a radio communicationunit 110, a signal processing unit 150, a control unit 160, and ameasuring unit 170.

(Radio Communication Unit)

The radio communication unit 110 performs radio communication with thebase station 200 on a communication channel formed by integrating aplurality of component carriers by using the carrier aggregationtechnology. Data signals transmitted to or received from the basestation 200 are, as will be further described below, data signalsinterleaved in accordance with channel quality for each componentcarrier or available situations of communication resources for eachcomponent carrier.

For example, as shown in FIG. 4, the radio communication unit 110includes an interleaver 112 and a deinterleaver 114. The interleaver 112interleaves bit strings of a data signal input from the signalprocessing unit 150 under the control of the control unit 160. Then, theradio communication unit 110 sends out a data signal interleaved by theinterleaver 112 onto a communication channel to the base station 200. Onthe other hand, the deinterleaver 114 deinterleaves bit strings of adata signal received via a communication channel to the base station 200under the control of the control unit 160. Then, the radio communicationunit 110 outputs a data signal deinterleaved by the deinterleaver 114 tothe signal processing unit 150.

(Signal Processing Unit)

The signal processing unit 150 performs signal processing such asdecoding and error corrections on a data signal input from the radiocommunication unit 110. Then, the signal processing unit 150 outputs aprocessed data signal to an upper layer. The signal processing unit 150also performs signal processing such as encoding on a data signal inputfrom an upper layer. Then, the signal processing unit 150 outputs aprocessed data signal to the radio communication unit 110.

(Control Unit)

The control unit 160 controls functions of the terminal apparatus 100 asa whole by using a processing unit such as a CPU (Central ProcessingUnit) and DSP (Digital Signal Processor). For example, the control unit160 controls the timing of data communication by the radio communicationunit 110 according to scheduling information received by the radiocommunication unit 110 from the base station 200. The control unit 160also causes the measuring unit 170 to measure channel quality of eachcomponent carrier (more suitably, each Resource Block in each componentcarrier) by using a reference signal from the base station 200 totransmit a channel quality report to the base station 200 via the radiocommunication unit 110. The control unit 160 also receives controlinformation about mapping between each component carrier and the QoSclass of each data signal from the base station 200 via the radiocommunication unit 110. The control information may be the sameinformation as the above scheduling information or differentinformation. Then, the control unit 160 controls processing of theinterleaver 112 or the deinterleaver 114 of the radio communication unit110 according to the control information.

(Measuring Unit)

The measuring unit 170 measures channel quality by using a referencesignal from the base station 200, for example, under the control of thecontrol unit 160. A measurement result by the measuring unit 170 isconverted into a predetermined format by the control unit 160 andtransmitted to the base station 200 via the radio communication unit110. A measurement result of the channel quality is used for mappingbetween each component carrier and the QoS class of each data signal inthe base station 200.

[2-2. Configuration Example of Base Station]

FIG. 5 is a block diagram exemplifying the configuration of the basestation 200 according to the present embodiment. Reference to FIG. 5shows that the base station 200 includes a radio communication unit 210,an interface unit 250, a storage unit 260, a quality acquisition unit268, a control unit 270, and a QoS management unit 280.

(Radio Communication Unit)

The radio communication unit 210 performs radio communication with theterminal apparatus 100 on a communication channel formed by integratinga plurality of component carriers by using the carrier aggregationtechnology. The radio communication unit 210 includes an interleaver 212and a deinterleaver 214. The interleaver 212 interleavs bit strings of adata signal input from the interface unit 250 under the control of thecontrol unit 270. Then, the radio communication unit 210 sends out adata signal interleaved by the interleaver 212 onto a communicationchannel to the terminal apparatus 100. On the other hand, thedeinterleaver 214 deinterleaves bit strings of a data signal receivedvia a communication channel to the terminal apparatus 100 under thecontrol of the control unit 270. Then, the radio communication unit 210outputs a data signal deinterleaved by the deinterleaver 214 to theinterface unit 250.

FIG. 6 is a block diagram exemplifying a detailed configuration of theradio communication unit 210. Reference to FIG. 6 shows that the radiocommunication unit 210 includes an antenna 216, an LNA (Low NoiseAmplifier) 220, a plurality of down-converters 222 a to 222 c, aplurality of filters 224 a to 224 c, a plurality of ADC (Analogue toDigital Converter) 226 a to 226 c, a demodulation unit 228, thedeinterleaver 214, the interleaver 212, a modulation unit 230, aplurality of DAC (Digital to Analogue Converter) 232 a to 232 c, furthera plurality of filters 234 a to 234 c, a plurality of up-converter 236 ato 236 c, a synthesizer 238, a PA (Power Amplifier) 240, and an antenna242.

When a radio signal transmitted from the terminal apparatus 100 isreceived, the antenna 216 outputs the received signal to the LNA 220.The LNA 220 amplifies the received signal. The down-converter 222 a andthe filter 224 a separate a baseband signal of a first component carrier(CC1) from the received signal amplified by the LNA 220. Then, theseparated baseband signal is converted into a digital signal by the ADC226 a and output to the demodulation unit 228. Similarly, thedown-converter 222 b and the filter 224 b separate a baseband signal ofa second component carrier (CC2) from the received signal amplified bythe LNA 220. Then, the separated baseband signal is converted into adigital signal by the ADC 226 b and output to the demodulation unit 228.Also, the down-converter 222 c and the filter 224 c separate a basebandsignal of a third component carrier (CC3) from the received signalamplified by the LNA 220. Then, the separated baseband signal isconverted into a digital signal by the ADC 226 c and output to thedemodulation unit 228. Subsequently, the demodulation unit 228 generatesa data signal by demodulating the baseband signal of each componentcarrier and outputs the data signal to the deinterleaver 214. Thedeinterleaver 214 deinterleaves the data signal input from thedemodulation unit 228 and outputs the deinterleaved data signal to thesignal processing unit 250.

If a data signal is input from the signal processing unit 250, theinterleaver 212 interleaves the data signal and outputs the interleaveddata signal to the modulation unit 230. The modulation unit 230modulates the data signal input from the interleaver 212 to generate abaseband signal for each component carrier. The baseband signal of thefirst component carrier (CC1) among these baseband signals is convertedinto an analog signal by the DAC 232 a. Then, a frequency componentcorresponding to the first component carrier of a transmission signal isgenerated by the filter 234 a and the up-converter 236 a from the analogsignal. Similarly, the baseband signal of the second component carrier(CC2) is converted into an analog signal by the DAC 232 b. Then, afrequency component corresponding to the second component carrier of thetransmission signal is generated by the filter 234 b and theup-converter 236 b from the analog signal. Also, the baseband signal ofthe third component carrier (CC3) is converted into an analog signal bythe DAC 232 c. Then, a frequency component corresponding to the thirdcomponent carrier of the transmission signal is generated by the filter234 c and the up-converter 236 c from the analog signal. Subsequently,frequency components corresponding to the three generated componentcarriers are synthesized by the synthesizer 238 to form a transmissionsignal. The PA 240 amplifies the transmission signal and then outputsthe transmission signal to the antenna 242. Then, the antenna 242transmits the transmission signal to the terminal apparatus 100 as aradio signal.

The radio communication unit 110 of the terminal apparatus 100 shown inFIG. 4 is configured in the same manner as the configuration of theradio communication unit 210 of the base station 200 described by usingFIG. 6, though requirements such as processing performance aredifferent.

In FIG. 6, an example in which the radio communication unit 210 handlesthree component carriers is described, but the number of componentcarriers handled by the radio communication unit 210 may be two or fouror more. Also in FIG. 6, an example in which the radio communicationunit 210 has one receiving antenna 216 and one transmitting antenna 242is described. However, the radio communication unit 210 may beconfigured to have a plurality of the receiving antennas 216 and aplurality of the transmitting antennas 242 to handle a plurality of MIMO(Multiple Input Multiple Output) streams.

(Interface Unit)

Returning to FIG. 5, the description of the example of the configurationof the base station 200 will continue. The interface unit 250 mediatescommunication between the radio communication unit 210, the control unit270, and the QoS management unit 280 and an upper node via, for example,the S1 interface illustrated in FIG. 1. The interface unit 250 mediatescommunication between the radio communication unit 210, the control unit270, and the QoS management unit 280 and other base stations via, forexample, the X2 interface illustrated in FIG. 1.

(Storage Unit)

The storage unit 260 holds CC management data indicating which componentcarrier is used by each terminal apparatus to perform communication foreach terminal apparatus belonging to the cell of the base station 200 byusing a storage medium such as a hard disk and semiconductor memory. TheCC management data can be updated by the control unit 270 when a newterminal apparatus participates in the cell of the base station 200 oran existing terminal apparatus changes the component carrier. Therefore,the control unit 270 can know which component carrier the terminalapparatus 100 muses by referring to the CC management data.

The storage unit 260 also holds QoS data indicating attribute valuessuch as the error rate, transfer delay, and guaranteed bit rate for eachQoS class to be met by traffic. The QoS data is used to decide mappingbetween each component carrier and the QoS class of each data signalwhen communication resources are scheduled.

(Quality Acquisition Unit)

The quality acquisition unit 268 acquires channel quality for eachcomponent carrier of communication channels to the terminal apparatus100. For example, the quality acquisition unit 268 may acquire a channelquality report transmitted from the terminal apparatus 100 via the radiocommunication unit 210. Instead, the quality acquisition unit 268 mayacquire channel quality for each component carrier by measuring thepower level, error rate and the like of a received signal in the radiocommunication unit 210. The quality acquisition unit 268 outputs thevalue of channel quality of each component carrier to the control unit270.

(Control Unit)

The control unit 270 controls functions of the base station 200 as awhole by using a processing unit such as a CPU and DSP. For example, thecontrol unit 270 schedules communication resources for data transmissionby the terminal apparatus 100 based on attribute values for each QoSclass to be met by traffic notified from the QoS management unit 280. Atthis point, the control unit 270 decides mapping between each componentcarrier and the QoS class of each data signal in accordance with channelquality for each component carrier acquired by the quality acquisitionunit 268 and available situations of communication resources for eachcomponent carrier. Three typical patterns (six variations) of suchmapping will further be described later by citing examples.

The control unit 270 controls interleave processing by the interleaver212 or deinterleave processing by the deinterleaver 214 of a data signaltransmitted on a communication channel to the terminal apparatus 100 inaccordance with a result of mapping between each component carrier andthe QoS class of each data signal. Three examples of the configurationof interleave processing by the interleaver 212 will further bedescribed later by citing examples.

(QoS Management Unit)

The QoS management unit (also called a QoS manager) 280 commonly managesQoS requirements to be met by traffic by using, for example, QoS dataheld by the storage unit 260. The QoS management unit 280 notifies thecontrol unit 270 of QoS requirements for data signals to be scheduledbefore communication resources being scheduled. If there is apossibility that QoS requirements are not met, the QoS management unit280 may negotiate with other base stations or an upper node so that QoSrequirements can be met by changing the path of RAN (Radio AccessNetwork) or utilizing a wire link.

Instead of being arranged in the base station 200, the QoS managementunit 280 may be arranged in an upper node of the base station 200. Theupper node of the base station 200 is a node corresponding to, forexample, a serving gateway or MME.

[2-3. Configuration Example of Interleave Processing]

Next, three examples of the configuration of interleave processing bythe interleaver 212 will be described by using FIGS. 7A to 7C.Incidentally, deinterleave processing by the deinterleaver 214 can beconfigured as processing in the opposite direction of the interleaveprocessing. From the viewpoint of avoiding redundancy of description, adetailed description of deinterleave processing is omitted.

First Example

First, reference to FIG. 7A shows the configuration of the interleaver212 a that frequency-interleaves (CC-interleaves) a data signal among aplurality of component carriers. In the example of FIG. 7A, theinterleaver 212 a interleaves first to sixth bits equally one bit afteranother among three component carriers. As a result, the first andfourth bits are distributed to the first component carrier, the secondand fifth bits are distributed to the second component carrier, and thethird and sixth bits are distributed to the third component carrier.

If, for example, available resources exceeding a certain ratio arepresent and a plurality of component carriers maintaining apredetermined quality level is available, the control unit 270 mayequally distribute each data signal among such component carriersregardless of the QoS class. Accordingly, interleave control issimplified to reduce the load of processing and also an effect ofimproved link characteristics by interleaving can be expected. Also, forexample, the control unit 270 may not distribute a data signalclassified into a class in which relatively high service quality isrequired to a component carrier, among the three component carriers,that does not maintain the predetermined quality level. The class inwhich relatively high service quality is required may be, for example,the “Conversational” class or the “Streaming” class shown in Table 1.Accordingly, an effect of improved link characteristics by interleavingcan be expected from a data signal on which stringent (or high-priority)QoS requirements are imposed while avoiding risk of violating QoSrequirements. The control unit 270 can cause the interleaver 212 toperform the above interleave processing by, for example, outputting acontrol signal S1 a to the interleaver 212.

Second Example

Reference to FIG. 7B shows the configuration of the interleaver 212 bthat time-interleaves (bit-interleaves) before a data signal beingfrequency-interleaved. In the example of FIG. 7B, the order of the firstto fourth bits is rearranged to the order of the fourth, first, third,and second bits. Then, these four bits are frequency-interleaved amongthree component carriers. As a result, the fourth and second bits aredistributed to the first component carrier, the first bit is distributedto the second component carrier, and the third bit is distributed to thethird component carrier.

Thus, by performing the time-interleave, in addition to thefrequency-interleave, for example, a weakened effect of improvedcharacteristics by frequency-interleaving when the number of availablecomponent carriers is smaller (for example, than a predeterminedreference value) can be compensated for. Available component carriersmean, for example, component carriers maintaining a predeterminedquality level and having sufficient available communication resources.Therefore, if, for example, the number of available component carriersis judged to fall below the predetermined reference value, the controlunit 270 may cause the interleaver 212 b to time-interleave each datasignal.

The pattern of rearranging bits in the time-interleave is, for example,defined as communication specifications in advance. Accordingly, forexample, bit strings interleaved by the interleaver 212 of the basestation 200 can be deinterleaved by the deinterleaver 114 of theterminal apparatus 100.

Third Example

Reference to FIG. 7C shows the configuration of the interleaver 212 cthat space-interleaves (stream-interleaves to a plurality of MIMOstreams) after a data signal being frequency-interleaved. In the exampleof FIG. 7C, the first to sixth bits are equally interleaved one bitafter another among three component carriers. As a result, the first andfourth bits are distributed to the first component carrier, the secondand fifth bits are distributed to the second component carrier, and thethird and sixth bits are distributed to the third component carrier.Further, among bits distributed to the first component carrier, thefirst and fourth bits are distributed to different MIMO streams.Similarly, among bits distributed to the second component carrier, thesecond and fifth bits are distributed to different MIMO streams. Also,among bits distributed to the third component carrier, the third andsixth bits are distributed to different MIMO streams.

Thus, also by performing the space-interleave, in addition to thefrequency-interleave, for example, a weakened effect of improvedcharacteristics by frequency-interleaving when the number of availablecomponent carriers is smaller (for example, than a predeterminedreference value) can be compensated for. Therefore, if, for example, thenumber of available component carriers is judged to fall below thepredetermined reference value, the control unit 270 may cause theinterleaver 212 c to space-interleave each data signal to a plurality ofMIMO streams using a plurality of MIMO antennas.

The pattern of distributing bits to MIMO streams in the space-interleaveis, for example, defined as communication specifications in advance.Accordingly, for example, bit strings interleaved by the interleaver 212of the base station 200 can be deinterleaved by the deinterleaver 114 ofthe terminal apparatus 100.

The frequency-interleave, time-interleave, and space-interleavedescribed by using FIGS. 7A to 7C are not limited to combinationsdescribed herein and can be used in any combination. For example, theinterleaver 212 may be configured to perform all of thefrequency-interleave, time-interleave, and space-interleave. Also, otherprocessing may be interposed between the interleave processing. Forexample, it is clear that encoding processing or the like may beperformed in the timing between the time-interleave and thefrequency-interleave or between the frequency-interleave and thespace-interleave.

[2-4. Mapping Between Component Carriers and Classes]

Next, typical patterns of mapping between each component carrier and theQoS class of each data signal will be described by using FIGS. 8 to 10D.

(First Pattern)

FIG. 8 is an explanatory view illustrating a first pattern (pattern P1)of mapping between each component carrier and the QoS class of each datasignal. The first pattern is a pattern that can be adopted when a datasignal to be transmitted contains data bits of a single QoS class.

Reference to FIG. 8 shows that the data signal contains only data bitsbelonging to the class C1. The control unit 270 of the base station 200distributes such data bits equally or non-equally among componentcarriers. In the example of FIG. 8, Resource Blocks in the componentcarriers CC1, CC2, CC3 are scheduled non-equally in the ratio of 3:2:1respectively. Such a ratio can be decided in accordance with channelquality of each component carrier or available situations of resource(for example, more bits are distributed to a component carrier in goodquality or a component carrier with more available resources).

(Second Pattern)

FIG. 9 is an explanatory view illustrating a second pattern (pattern P2)of mapping between each component carrier and the QoS class of each datasignal. The second pattern is a pattern that can be adopted when a datasignal to be transmitted contains data bits of a plurality of QoSclasses.

Reference to FIG. 9 shows that the data signal contains data bitsbelonging to the classes C1, C2, C3. The control unit 270 of the basestation 200 distributes these data bits to each component carrier sothat data bits classified into different classes are transmitted onmutually different component carriers. If, for example, QoS requirementsof the class C1 are the most stringent (the highest priority), thecontrol unit 270 allocates data bits belonging to the class C1 to thecomponent carrier CC1 in the best channel quality. Also, the controlunit 270 allocates data bits belonging to the class C2 whose QoSrequirements are the second most stringent (the second highest priority)to the component carrier CC2 in the second best channel quality.Further, the control unit 270 allocates data bits belonging to the classC3 whose QoS requirements are the most lax to the remaining componentcarrier CC3. According to the second pattern described above, only datasignals belonging to one QoS class are transmitted on one componentcarrier and thus, costs needed for QoS management are reduced.

(Third Pattern)

FIGS. 10A to 10D are explanatory views illustrating a third pattern ofmapping between each component carrier and the QoS class of each datasignal. The third pattern is, like the second pattern, a pattern thatcan be adopted when a data signal to be transmitted contains data bitsof a plurality of QoS classes. In the third pattern, however, data bitsclassified into mutually different classes are distributed to the commoncomponent carrier. Four variations of the third pattern, that is,patterns P3 a to P3 d will be described one by one below.

Reference to FIG. 10A (pattern P3 a) shows that the data signal containsdata bits belonging to the classes C1, C2, C3. The control unit 270 ofthe base station 200 distributes these data bits to each componentcarrier in the same ratio. That is, the ratio of data bits distributedto the component carrier CC1 and belonging to the classes C1, C2, C3 isequal to the ratios for the component carriers CC2, CC3. According tothe pattern P3 a, the distribution of data bits can be decided by thecommon ratio and thus, mapping processing is simplified and processingcosts for scheduling can be reduced. Moreover, due to an effect of thefrequency-interleave, better link characteristics can be obtained whencompared with a case when data bits belonging to the same class aresimply distributed to the same component carrier.

Reference to FIG. 10B (pattern P3 b) shows that the data signal containsdata bits belonging to the classes C1, C2, C3. The control unit 270 ofthe base station 200 distributes these data bits in a ratio differentfrom component carrier to component carrier. In the example of FIG. 10B,data bits belonging to the classes C1, C2, C3 are distributed to thecomponent carrier CC1. On the other hand, only data bits belonging tothe class C1 are distributed to the component carrier CC2. Also, onlydata bits belonging to the classes C2, C3 are distributed to thecomponent carrier CC3. According to the pattern P3 b, the quantity ofcommunication resources allocated to each component carrier can beincreased or decreased in accordance with stringency (priority level) ofQoS requirements. Therefore, more flexible scheduling is enabled inorder to meet the QoS requirements.

Reference to FIG. 10C (pattern P3 c) shows that the data signal containsdata bits belonging to the classes C1, C2, C3. The control unit 270 ofthe base station 200 distributes these data bits to one componentcarrier. The pattern P3 c can be adopted when channel quality of onecomponent carrier is far better than channel quality of other componentcarriers and sufficient resources are available.

Reference to FIG. 10D (pattern P3 d) shows that the data signal containsdata bits belonging to the classes C1, C2, C3. The control unit 270 ofthe base station 200 distributes these data bits in a ratio differentfrom component carrier to component carrier. In the pattern P3 d, incontrast to the pattern P3 b shown in FIG. 10B, the control unit 270distributes data bits belonging to different classes to one ResourceBlock. In the example of FIG. 10D, data bits belonging to the classesC1, C2, C3 are distributed to the component carrier CC2. Then, data bitsbelonging to the classes C1, C2 are distributed to a Resource Block RB1of the component carrier CC2. Also, data bits belonging to the classesC1, C3 are distributed to a Resource Block RB2 of the component carrierCC2. According to the pattern P3 d, more flexible scheduling is enabledin accordance with quality in units of Resource Blocks.

(Selection of Mapping Patterns)

When scheduling communication resources, the control unit 270 can make aselection of which pattern of the above patterns to adopt in accordancewith variations in channel quality of each component carrier oravailable situations of resources for each component carrier. Table 2shows an example of selection criteria of the mapping pattern. Here, acase when a data signal to be transmitted contains data bits of aplurality of QoS classes will mainly be described.

TABLE 2 Example of selection criteria of the mapping pattern AvailableVariations in quality situations of All CCs meet Some CCs do not meetresources predetermined criteria predetermined criteria All CCs meetCase 1-1 Case 1-2 predetermined (Single class → P1) Pattern P3d criteriaA plurality of classes → Pattern P2 or P3a Some CCs do Case 2-1 Case 2-2not meet Pattern P3b Pattern P3c predetermined criteria

In Table 2, available situations of resources are evaluated based on,for example, the availability of resources for each component carrier.Variations in quality are evaluated based on, for example, channelquality for each component carrier obtained through a channel qualityreport.

As available situations of resources, for example, it is assumed thatthe availability falls short of a predetermined ratio (that is,sufficient resources are available) for all component carriers. Further,if channel quality of all component carriers exceeds predeterminedcriteria, the control unit 270 can select the pattern P2 or the patternP3 a (case 1-1). Among these patterns, if it is desirable, for example,to reduce costs needed for QoS management, the pattern P2 is selected.If it is desirable, instead, to improve link characteristics, thepattern P3 a may be selected.

If available situations of resources are similar to the case 1-1 and acomponent carrier whose channel quality does not meet predeterminedcriteria is present, the control unit 270 can select the pattern P3 d(case 1-2).

If a component carrier whose availability exceeds predetermined criteria(that is, sufficient resources are not available) is present and channelquality of all component carriers exceeds predetermined criteria, thecontrol unit 270 can select the pattern P3 b (case 2-1). If availablesituations of resources are similar to the case 2-1 and a componentcarrier whose channel quality does not meet predetermined criteria ispresent, the control unit 270 can select the pattern P3 c (case 2-2).

The control unit 270 of the base station 200 decides mapping betweeneach component carrier and the QoS class of each data signal based onthe selection criteria as an example. Then, the control unit 270transmits control information concerning the mapping to the terminalapparatus 100 via the radio communication unit 210. The controlinformation concerning the mapping may be, for example, schedulinginformation delivered on a control channel or broadcast channel of adownlink. The control information concerning mapping suitably representsmapping between a Resource Block contained in each component carrier andthe QoS class of each data signal transmitted in the Resource Block. Thecontrol information concerning mapping may also contain, for example,identification code that can identify the pattern of the adopted mappingand the pattern of interleaving.

Accordingly, the control unit 160 of the terminal apparatus 100 cancontrol the interleaver 112 or the deinterleaver 114 of the radiocommunication unit 110 according to the control information transmittedfrom the base station 200. The control unit 270 also controls theinterleaver 212 or the deinterleaver 214 of the radio communication unit210 in accordance with mapping between each component carrier and theQoS class of each data signal.

5. Conclusion

Heretofore, the radio communication system 1 according to an embodimentof the present invention has been described by using FIGS. 1 to 10D.According to the present embodiment, a data signal transmitted on acommunication channel formed by carrier aggregation technology isinterleaved in the base station 200 in accordance with channel qualityfor each component carrier and available situations of communicationresources for each component carrier. That is, interleaving is performedadaptively in accordance with communication channel conditions and thus,the certainty with which an effect of interleaving can be enjoyed isincreased. As a result, communication characteristics are improved to beable to maintain a high service quality. Because thefrequency-interleave, time-interleave, and space-interleave are usedcomplementarily, the service quality level can be maintained even insituations when an effect of the frequency-interleave between componentcarriers cannot be expected much.

It does not matter whether a sequence of processing according to anembodiment described herein is realized by hardware or software. If asequence of processing or a portion thereof is performed by software, aprogram constituting the software is stored in a hard disk or a storagemedium such as a semiconductor memory and is read into a RAM (RandomAccess Memory) during execution before being executed by a processingunit such as a CPU and DSP.

The preferred embodiments of the present invention have been describedabove with reference to the accompanying drawings, whilst the presentinvention is not limited to the above examples, of course. A personskilled in the art may find various alternations and modificationswithin the scope of the appended claims, and it should be understoodthat they will naturally come under the technical scope of the presentinvention.

REFERENCE SIGNS LIST

-   1 Radio communication system-   100 Terminal apparatus-   110 Radio communication unit-   160 Control unit-   200 Base station-   210 Radio communication unit-   212 Interleaver-   214 Deinterleaver-   268 Quality acquisition unit-   270 Control unit-   280 QoS management unit

1. A user equipment that performs radio communication with a basestation on at least a downlink communication channel including aplurality of component carriers, the user equipment comprising:circuitry configured to receive a data signal on the downlinkcommunication channel, the data signal having been classified to atleast one of a plurality of classes according to a service quality andassigned to at least one component carrier of the plurality of componentcarriers based on the class of the data signal and the service quality,and at least one bit of the data signal received on the downlinkcommunication channel having been allocated to the at least onecomponent carrier in which the data signal is assigned.